React Performance Optimization

React is fast by default, but complex applications can develop performance bottlenecks as component trees grow. Understanding when and why React re-renders is the foundation of any optimization work.

Memoization with useMemo and useCallback

Use useMemo to cache expensive computed values between renders. Use useCallback to stabilize function references passed as props to child components. Apply these only when profiling shows a real problem — premature optimization adds complexity without benefit.

React.memo for Component Memoization

Wrap pure functional components with React.memo to skip re-rendering when props have not changed. This is most effective for components that receive the same props frequently and are expensive to render.

Virtualization for Long Lists

Rendering thousands of DOM nodes at once is expensive. Libraries like react-window or TanStack Virtual render only the visible rows, keeping the DOM lean regardless of list size.